Austenitic chromium nickel steel alloy



Patented Feb. 13, 1940 v I v I UNITED 'STATES PATENT OFFICE PaulSchafmeister, Essen, Germany, assignor, by mesne assignments, to KruppNirosta 00., Inc., New York, N. Y., a corporation of Delaware NoDrawing. Application July 11, 1931, Serial No. 550,288. Renewed July 20,1939. In Germany July 21, 930

18 Claims. (Cl. 75-128) Experience has shown that austenitic chro notbecome brittle when they have experienced mium nickel steel alloys thusfar used for corroheating to about 500 to 900C. sion-resting materialcease to be resistant against It is especially-advantageous to use asthe added attack by chemical agents, lose their metallic alloy componentone or both of the elements ring, become brittle, and finally evencrumble columbium and tantalum, since these elements 5 to metal powderwhen they are exposed to a heat not only combine with the carbon in amanner treatment comparable to a drawing treatment of which does notdeleteriously affect the chemical approximately between 500 to 900 C'.,as, for inand mechanical stability of the alloy but they stance, inwelding together of individual strucfurthermore result in particularlygood welding tural sections or in use, as for instance, in aproconditions. The loss due to burning off of the m cess ofhydrogenation. It has already been proelements columbium and tantalumduring weldposed with considerable success that for the purng is onlyvery Small and in fact Smaller than pose of making articles ofaustenitic chromium that of other elements such as zirconium, urannickelsteel alloys which either in their manufacium, hafnium, cerium, thorium,lanthanum,

ture or use are exposed to a temperature compay u neodymium. Samarium,other rare rable to a drawing treatment, austenitic chroearth metals,any one or more of which may be mium nickel steel alloys should be usedwhose carused with columbium or tantalum, or both, to bon content isbelow 0.07% or which contain 'sineffect the purpose of my invention, asthe advangly or together elements such as titanium or vatage of myinvention is, at least to a certain exnadium which form stable chemicalcombinations tent, inherent also in the use of such other elel0 withcarbon, the relation between titanium, rements. spectively vanadium, tothe carbon being prefer-, The iron content of the alloys forming thesubably such that practically the entire carbon enters jest-matter ofthe invention may be as low as into the inter-combination with the addedele- 50%, or even lower.

ments. The chromium content of the-alloy'may be of '25 I have found thatit is not only the type of t e order of approximately 12% to 40%, the

chromium nickel steel alloys having a stable nickel content of the alloymay be of the order surface that is to say, austenitic chromium nickelof approximately 7% to 25%, while the carbon steel alloys .whicheitherhave a carbon content contenti's preferably less than 1%. In the preofless than about 0.07% or contain, for example, 'ferred embodiment of theinvention, the alloy '80 titanium, and/or vanadium which have theadcontains about 18% chromium, 8% nickeL'bevantage that they do not losetheir resistance to tween 07% and 2% carbon, and columbium or corrosiveagents and do not become brittle when tantalum. or a mixture of theseelements, about in manufactureor use they are exposed to tem- 3% to2.5%. The added element or elemen s peratures comparable to drawingtreatments of may be used up to 10%, and should be present in '35 about500 to 900 C., but that this advantage is amounts at least suflicient tobind practically also inherent in austenitic chromium nickel steelall'the carbon contained in the alloy. alloys which contain one or moreof the elements Austenitic chromium nickel steel, alloys, of thecolumbium (niobium) and tantalum. These eletype to which the presentinvention relates, are

40 ments also, as has been proven, form such a v in themselves wellknown and, as ordinarily used, '0 stable chemical combination with thecarbon in contain about 12%-30% chromium. (preferably solution in theaustenitic base mass that the inthe neighborhood of 18%), about 7% to.25% chemical-and mechanical stability of the alloy nickel (preferably inthe neighborhood of 8%), is not affected for practical purposes after .aheat carbon from about 07% to about .2%, and iron,

all treatment of about 500 to 900 C. In these constituting substantiallythe entire balance 43 cases, as in the case of titanium and vanadium,(with the exception of normal impurities), the it is alsoadvantageous-to establish such a relairon being substantially all in thegamma form. tion of the stated alloy components with respect One of theprincipal uses of these alloysis in to the carbon that practically theentire amount the production of chemical apparatus of various 0 ofcarbon is bound to the added alloy components. types, in which sheets orplates, made of the Te ts with chromium nickel steel alloys havingaalloy, are united by fusion welding. These alloys, stable surface andcontaining about 0.17% carhowever, if exposed to elevated temperaturesor bon, 8% nickel, 18% chromium, 1.3% tantalum the approximate range of500 to 900 C., for inplus columbium, show that such alloys still pre-'stance by uniting individual parts thereof by u serve their resistanceto corrosive attack and do fusion welding, and then exposed to corrosiverosion. If they are exposed, for any appreciable length of time, to suchtemperaturerange, chi-o .mium carbides will precipitate 'therein,robbing the grain boundaries of their protective chromium, thuspermitting intergranular corrosion to occur. The temperaure rangespecified .may therefore be termed the carbide precipitation range,. Thedifliculty caused by the formation of these carbides, could be cured, aswas known, by reheating the metal to a temperature of 1000 C. or higher,and then rapidly cooling it. Such a process is, however, impracticable,if not impossible, with larger articles, not only because it isdiflicult, or impossible to heat themto-the necessary high temperature,and then to cool them rapidly, but also because of the liability ofdistortion of the article, by its own weight, while the metal is in asoftened condition.

It should be kept in mind that my invention includes articles made ofaustenitic chromium nickel steel alloys, to which have been addedcolumbium or tantalum, or both, as equivalent substances,-for thepurpose of combining with substantially all of the carbon present, sothat the carbon will not be able to combine with the chromium, thuspreventing intergranular corrosion when the alloy is subjected to thetemperature range (carbide precipitation range) specified, without beingthereafter necessarily further heat treated. By way of example, myalloys will thus, even on prolonged heating at a temperature such as 500C., lessen materially loss of corrosion resistance.

The alloys, containing one or both of these addition materials, maytherefore, as hereinabove stated, be used in the manufacture of metalarticles, including fusion welded articles, which, in their normal use,are subjected to active corrosive influences, while the metal in atleast a part thereof is in a condition resulting from heating, forinstance, by fusion welding, at ranges within the carbide precipitationrange, without the necessity of curing, that is, without subsequentheating at substantially higher temperatures (and then rapidly cooling);and such articles will nevertheless be resistant to corrosiveinfluences,

that is, will not be subject to intergranular 'cor-,

rosion.

Any departure from the proportions specified in my claims which may,however, result in an alloy which exhibits the advantages of myinvention, even though in a less effective manner, would still be withinthe spirit of my invention, and of the scope of my claims.

Articles made of the alloy hereinabove described containing zirconium asthe addition material. are claimed in my divisional application Ser. No.227,689, issued May 2, 1939, as Patent No. 2,157.060.

I claim:

1. A corrosion-resisting steel alloy containing about 12% to 30%chromium, about 7% to 25% nickel. carbon in appreciable quantity butless than 1%, and an additional material acting to lessen materiallyloss of corrosion resistance on prolonged holding at 500 C., in anamount sufllcient to combinev with substantially all of the carbon butnot in excess of 10%, the balance being substantially all iron, suchadditional material consisting substantially all of columbium.

' 2. A corrosion-resisting steel alloy containing about 12% to 30%chromium, about 7% to 25% nickel, about 0.07% to 0.2% carbon, and from v2,190,486 conditions, become liable to intergranular cor-" lessenmate'rially loss of corrosion resistance on prolonged holding at 500 0.,the balance substantially all iron, saidadditional material consistingsubstantially all of. columbium.

3. A corrosion-resisting steel alloy containing about 18% chromium,about 8% nickel, .07% to .2% carbon and from'.3% to 2.5% ofa'nadditional material acting to lessen materially loss of corrosionresistance on prolonged holding at 500 C., the balance substantially alliron, said additional material consistingsubstantially all of columbium.

4. A fusion Welded article composed of an austenitic corrosion resistingsteel alloy containing about 12%to 30% chromium, about 7% to 25% nickel,carbon in appreciable quantity but less than 1%, and an additionalmaterial in amount suificient to combine with substantially all of thecarbon but not in excessof 10%; said additional material being at leastone of the elements of the group consisting of columbium and tantalum,the balance being substantially all iron. I

5. A fusion welded article composed of an aus' tenitic corrosionresisting steel alloy containing about 12% to 30% chromium, about 7% to25% nickel, about .07% to .2% carbon, and about .3% to 2.5% of anadditional material acting to lessen materially loss of corrosionresistance, the balance being substantially all iron, said additionalmaterial being at least one of the elements of the group consisting ofcolumbium and tantalum.

6. A fusion welded article composed of an austenitic corrosion resistingsteel alloy containing about 18% chromium, about 8% nickel, about .07%to .2% carbon, and about .3% to 2.5% of an additional material acting tolessen materially loss of corrosion resistance, the balance beingsubstantially all iron, said additional material being at least one ofthe elements of the group consisting of columbium and tantalum.

7. A fusion-welded article composed of an austenitic corrosion-resistingsteel alloy containing about 12% to 30% chromium, about 7% to 25%nickel, carbon in appreciable quantity but less than 1%, and anadditional material in an amount sufficient to combine withsubstantially all of the carbon but not in excess of 10%, the

balance being substantially all iron, said additional materialconsisting substantially all of columbium.

8. A fusion-welded article composed of 'an austeniticcorrosion-resisting steel alloy containing about 12% to 30% chromium,about 7% to 25% nickel, about 0.07% to 0.2%. carbon, and from 0.3% to2.5% of an additional material acting to lessen materially loss ofcorrosion resistance, the balance substantially all iron, saidadditional material consisting substantially all of columbium.

9. A fusion-welded article composed of an austenitic corrosion-resistingsteel alloycontaining about 18% chromium, about 8% nickel, 0.07% to 0.2%carbon, and from 0.3% to 2.5% of an additional material acting to lessenmaterially loss of corrosion resistance, the balancesubstansubstantially all of columbium.

10. A fusion-welded article composed of an austeniticcorrosion-resisting steel alloy containing about 12% to 30% chromium,about 7% to 25% nickel, carbon in appreciable quantity but less than 1%,and an additional material in an amount suflicient to combine withsubstantially all of the carbon but not in excess of 10%, the

balance being substantially all iron, said additional materialconsisting substantially all of tantalum.

11. A fusion-welded article composed of an austeniticcorrosion-resisting steel alloy containing about 12% to 30% chromium,about 7% to 25% nickel, about 0.07% to 0.2% carbon, and

from 0.3% to 2.5% of an additional material acting to lessen materiallyloss of corrosion resistance, the balance substantially all iron, saidadditional material consisting substantially all oi tantalum.

12. A fusion-welded article composed of an austeniticcorrosion-resisting steel alloy containing about 18% chromium, about 8%nickel, 0.07% to 0.2% carbon, and from 0.3% to 2.5% of an additionalmaterial acting to lessen materially loss of corrosion resistance, thebalance substantially all iron, said additional material consistingsubstantially all of tantalum.

-13. A'fusion-welded article composed of anausteniticcorrosion-resisting steel alloy containing about 12% to 30%chromium, about 7% to 25% nickel, carbon in appreciable quantity butless than 1%, and an additional material in an amount sufficient tocombine with substantially all of the carbon but not in excess of 10%,the

balance being substantially all iron, said additional materialconsisting substantially all of columbium and tantalum.

14. A fusion-welded article composed of an austeniticcorrosion-resisting steel alloy containing about 12% to 30% chromium,about 7% to 25% nickel, about 0.07% to 0.2% carbon and from 0.3% to 2.5%of an additional material acting to lessen materially loss of corrosionresistance, the balance substantially all iron, said additional materialconsisting substantially all of columbium and tantalum.

15. A fusion-welded article composed of an austeniticcorrosion-resisting steel alloy containing about 18% chromium, about 8%nickel, 0.07% to 0.2%.carbo and from 0.3% to 2.5% of an additionalmaterial acting "to lessen materially loss of corrosion resistance, thebalance substantially all iron, said additional material consistingsubstantially all of columbium and tantalum.

16. A metal article which, in its normal use, is subjected to activecorrosive influences while the metal in at least part of the article isin a condition resulting from heating at ranges within the carbideprecipitation range (approximately 500 to 900 C.) without subsequentheating at substantially higher. temperatures, said article beingresistant to said corrosive influences and composed of acorrosion-resisting austenitic steel alloy, the iron of which issubstantially all in the gamma form, containing about 12% to 30%chromium, about 7% to 25% nickel, carbon in appreciable quantity butless than 1%, and columbiumin an amount sufllcient to combine withsubstantially all of the carbon but not in excess of 10%, the balancebeing substantially all iron.

17. A metal article which in its normal use is subjected to activecorrosive influences while the metal in at least part of the article isin a condition resulting from heating at ranges within the carbideprecipitation range (approximately 500 to 900 C.) without subsequentheating at substantially higher temperatures, said article beingresistant to said, corrosive influences and composed of a corrosionresisting austenitic steel alloy, the iron of which is substantially allin the gamma form, containing about 12% to 30% chromium, about 7% to 25%nickel, about .0'7% to .2% carbon, and from .3% to 2.5% of an additionalmaterial consisting substantially all of columbium, the balance beingsubstantially all iron.

18. A metal article which, in its normal use. is subjected to activecorrosive influences while the metal in at least part of the article isin a condition resulting from heating at ranges within the carbideprecipitation range (approximately 500 to 900 C.) without subsequentheating at substantially higher temperatures, said article beingresistant to said corrosive influences and composed of acorrosion-resisting austenitic steel alloy, the iron of which issubstantially all in the gamma iorm, containing about 18% chromium,about 8% nickel, about .07% to .2% car- 'bon and about .3% to 2.5%columbium, the balance being substantially all iron.

PAUL SCI-IAFMEISTER.

